Split cycle cryogenic cooler with rotary compressor

ABSTRACT

A rotary compressor providing modulated pressure pulses to a remotely located free displacer. The rotary compressor employs a novel modified Wankel-type mechanism in which two adjacent chamber regions are shorted to the crankcase of the device or to a bypass volume while the third chamber region develops the pressure pulses which are communicated to the free displacer by means of a valveless line.

tates Horn et al.

[ 1 Dec. 10, 1974 SPLIT CYCLE CRYOGENIC COOLER WITH ROTARY COMPRESSOR[75] Inventors: Stuart B. Horn, Fairfax; Buford T. Walters, Woodbridge,both of Va.

[73] Assignee: The United States of America as represented by theSecretary of the Army, Washington, DC.

[22] Filed: Oct. 18, 1973 [21] Appl. No.1 407,764

52 U.S. c1. 418/61, 62/6 [51 Int. Cl. F016 1/02 [58] Field 6: Search62/6; 418/61 A [56] References Cited UNITED STATES PATENTS 3,426,5252/1969 Rubin 62/6 3,509,718 5/1970 Fezer 62/6 3,647,327 3/1972 Manthey.418/61 3,765,187 10/1973 Horn 62/6 Primary Examiner-Williati1 J. Wye IAttorney, Agent, or FirmNathan Edelberg; Milton W. Lee; T. Major 57]ABSTRACT A rotary compressor providing modulated pressure pulses to aremotely located free displacer. The rotary compressor employs a novelmodified Wankel-type mechanism in which two adjacent chamber regions areshorted to the crankcase of the device or to a bypass volume while thethird chamber region develops the pressure pulses which are communicatedto the free displacer by means of a valveless line.

2 Claims, 3 Drawing Figures.

PAIENIED M 3.85%437 FIG. 2

SPLIT CYCLE CRYOGENIC COOLER WITH ROTARY COMPRESSOR The inventiondescribed herein may be manufactured, used, and licensed by or for theGovernment for governmental purposes without the payment to us of anyroyalty thereon.

BACKGROUND OF THE INVENTION Recent years have seen a great deal ofeffort directed to the development of cryogenic coolers for use withinfrared detectors. Since these detectors must undergo rapid scanningmotion for area surveillance, a cooler including a cold head of low massremotely located from the compressor is a necessity. A review of anumber of cryogenic devices and techniques can be found in applicationSer. No. 279,145 of Stuart B. Horn now U.S. Pat. No. 3,765,187.

SUMMARY OF THE INVENTION A remote cooler having a cold head for coolingan infrared detector and utilizing a free displacer is completelydescribed in the above noted application Ser. No. 279,145 now U.S. Pat.No. 3,765,187. The invention described in the instant applicationutilizes a similar free displacer and incorporates a novel Wankel-typemechanism for developing modulated pressure or pressure pulses in aworking gas, such as helium, between this mechanism and the remote freedisplacer which cause the free displacer to reciprocate and produce netrefrigeration by the process described in the incorporated reference.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows. the combination of therotary compressor and the remotely located free displacer; 7

FIG. 2 is a cross-sectional view of the rotary compressor;

FIG. 3 is a top view and cut-away of the compressor of FIG. 2 showingthe gearing and porting arrangement.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 diagrammatically showsthe rotary compressor 10, the remote cooler 11 with a free displacertherein and having-a cold head 12 and a connecting tube 13 through whichthe pressure waves generated by the compressor travel.

Turning to FIG. 2, a cross-section of the compressor can be seen. Thecompressor consists of a housing made up of a motor housing and therotor housing 21. The motor housing contains an electric motor 22 and issealed by end cap 23. A keyed drive shaft 24 is joined to a keyedrotorshaft 25 by a balancing sleeve 26, located in crankcase 27; whichsleeve provides dynamic balance to the system made necessary by theepitrochoidal motion of the rotor 28. Needle bearings 29 support therotor shaft 25.

carries a purging port 40 which permits the compressor to be purged andfilled with a working gas such as helium.

Turning to FIG. 3, the details of the novel compressor can be seen. Thechamber 33, carrying the rotor 28 therein, is formed by a two-lobedepitrochoid, peritrochoid or is generated by several arcs.

The rotor 28 having three sides and being generated from epitrochoid,peritrochoid, coordinate transformation or from arcs, divides thechamber volume 33 into three regions. Each of the vertices of the rotorretains a wiper seal 43 made of dry lubricated material such asgraphite-type plastic called Dupont Vespel. This results in a compressorthat is dry lubricated and thus free of condensible gases which mightotherwise impair the operation of the cooler section.

As can be seen here, three ports 30, 31 and 32 are located in thechamber 33 and are 'angularly' spaced apart. As was noted before, twoadjacent ports and 31 are shorted to the crankcase 27 or to some otherreservoir volume as would be appropriate to a particular design. Thisprevents gas compression on one side of the compressor chamber 33.

The port 32 is located in that region of the chamber wherein thepressure waves are developed. The waves are transmitted through thisport to the remote cooler 11 via the connecting tube 13.

The drive means for the rotor 28 comprises a ring gear 41 positionedcentrally of the rotor and the bearing 29 and a spur gear 42 centrallyfixed in the chamber volume 33; which gear 42 engages the ring gear 41.The drive shaft 24, powered by the motor 22, passes axially through thespur gear 42 and carries an eccentric lobe 44 which engages the rotor28. As the driveshaft 24 is turned, 'it drives the rotor in anepitrochoidal path.

course, that the pressure waves and free displacer rnotion are properlyphased to achieve the desired results.

While just one embodiment of the invention is herein disclosed it is tobe understood that many modifications may be made while remaining withinthe spirit and scope of the invention which is to be limited only by thefollowing claims.

We claim:

1. A rotary compressor for generating pressure pulses comprising:

a two-lobed chamber;

a rotor positioned in said chamber and coupled to a drive means forrotating said rotor in said chamber in an epitrochoidal path, said rotorhaving three arcuate sides and dividing said chamber into three volumeregions as it revolves;

three ports located in said chamber;

one of said ports, utilize as an output port far said pressure pulses,being located substantially at a perigee of the two-lobed chamber in aregion in which said pressure pulses are developed; and with one of eachof the other two remaining ports being located respectively in each lobeof the chamber; and I 2. The compressor of claim 1, wherein said commonvolume means comprises a crank case adjacent said,

chamber with which said two remaining ports communicate and are therebyshorted to prevent said pressure mon volume means to. prevent pressureincrease in 5 increase.

the regions of these two remaining ports.

1. A rotary compressor for generating pressure pulses comprising: atwo-lobed chamber; a rotor positioned in said chamber and coupled to adrive means for rotating said rotor in said chamber in an epitrochoidalpath, said rotor having three arcuate sides and dividing said chamberinto three volume regions as it revolves; three ports located in saidchamber; one of said ports, utilize as an output port far said pressurepulses, being located substantially at a perigee of the twolobed chamberin a region in which said pressure pulses are developed; and with one ofeach of the other two remaining ports being located respectively in eachlobe of the chamber; and the two remaining ports being angularly spacedabout said one of said ports with one of each of the remaining portsbeing located respectively in each lobe of the chamber and being shortedto a common volume means to prevent pressure increase in the regions ofthese two remaining ports.
 2. The compressor of claim 1, wherein saidcommon volume means comprises a crank case adjacent said chamber withwhich said two remaining ports communicate and are thereby shorted toprevent said pressure increase.